The researchers discuss the design of the next generation of M-Cube prototypes. (Photo : M. Scott Brauer)

It turns out that there may be a surprisingly simple method for creating self-assembling robots. MIT researchers have created M-Blocks, robots shaped like cubes, which can climb over and around one another, leap through the air and roll across the ground.

The M-blocks are cubes with no external moving parts. Instead, inside each M-Block is a flywheel that can reach speeds of 20,000 revolutions per minute. When the flywheel is braked, it imparts its angular momentum to the cube. In addition, on each edge of an M-Block and on every face are cleverly arranged permanent magnets. These magnets allow any two cubes to attach to one another.

"It's one of these things that the [modular-robotics] community has been trying to do for a long time," said Daniela Rus, one of the researchers, in a news release. "We just needed a creative insight and somebody who was passionate enough to keep coming at it--despite being discouraged."

Existing modular-robot systems are "statically stable." This means that you can pause the motion of the robot at any one point and they'll stay where they are. Yet in order to accomplish the feat of self-assembly, the researchers gave up on the principle of static stability.

"There's a point in time when the cube is essentially flying through the air," said Kyle Gilpin, one of the researchers, in a news release. "And you are depending on the magnets to bring it into alignment when it lands. That's something that's totally unique to this system."

In order to compensate for its static instability, the researchers employ magnets. The two cylindrical magnets on each edge of the cube are mounted like rolling pins. When two cubes approach each other, the magnets naturally rotate so that north poles align with south and vice versa. This allows any face of any cube to attach to the face of any other.

The researchers aren't done, though. They hope to potentially miniaturize these cubes in order to create microbots that can self-assemble. The result would be like the "liquid steel" androids in the movie "Terminator II." Currently, though, the MIT researchers are focusing on building an army of 100 cubes and designing algorithms to guide them.